yade-users team mailing list archive

[Václav Šmilauer <eudoxos@xxxxxxxx>]

> 1) PWave time step (could you give me some references on this, please)
> 
> 2) GSTS
> 
> 3) A fixed constant value set by the user
> 
> Now I am not sure that for the explicit scheme we are using and for
> the case of non linear relationship between forces and displacements
> (that is of my interest) we end up with the critical time step for the
> system using one of the above. Has anyone tested this aspect before?
> Do you have any references to suggest me that eventually touch this
> issue (if any)? 
> I am not even sure why, if I use the GSTS, I should give the
> tangential stiffnesses and not the secant values as input. 
> In summary, do you see any limit of applicability for the use of GSTS?

GSTS computes the "real" critical time step (based on numerical
stability of the integration scheme), whereas PWave only makes an
estimate. Particle oscillation is governed by current stiffness (that's
why you need tangent, i.e. current, stiffness).

If you have variable stiffness, you should set GTST safetyFactor and
interval to such values that you don't go over Δt even if running GSTS
only sometime. Actually, if you go over Δt on one interaction for short
time, you might not even notice in overall (explosion etc), as it will
locally stabilize later...

(For reference, I send you working copy of my thesis separately... I
know of no other ATM.)

Cheers, Vaclav